A data center refers to a suite of integrated Information Technology (IT) application environment that implements, in physical space, centralized processing, storage, transmission, exchange, and management of data. In a current data center network, deployment of a value-added service device, such as a firewall or an intrusion prevention system (IPS), is closely related to a network topology, and the close correlation between a value-added service and the network topology causes the deployment of the value-added service device to be extremely inflexible. Therefore, to flexibly deploy a value-added service device in a data center network, a service chaining technology is provided. The service chaining is a new mode of deploying a virtual service in a virtual and cloud-computing-based data center network.
As shown in FIG. 1, in an existing service chaining technology, a centralized delivery node (DN) is deployed in front of a server, where the centralized delivery node includes a distributed virtual switch, and each value-added service node (SN) is directly connected to the delivery node. The delivery node determines which traffic needs to be delivered to which value-added service nodes for processing and a service processing sequence. On a service chain from a client to the server shown in FIG. 1, the DN first sends a service flow to SN1; SN1 processes the service flow and returns the processed service flow to the DN; the DN then sends the service flow processed by SN1 to SN2, and SN2 processes the service flow and returns the processed service flow to the DN; the DN then sends the service flow processed by SN1 and SN2 to SN3, and SN3 processes the service flow and returns the processed service flow to the DN. In the foregoing manner, if one value-added service node is faulty, for example, when SN1 breaks down, the service chain from the client to the server is interrupted. It can be seen that, the service chain in the prior art has extremely low reliability.